Solid-state multinuclear magnetic resonance investigation of Pyrex®

Structure–property correlations in lead borate and borosilicate glasses doped with aluminum oxide

“…To maintain charge balance throughout the material, diboron trioxide undergoes a change in polymerization from three-coordinated ( [3] B) bridging species to a four-coordinated ( [4] B) bridging species with a negative charge delocalized over the tetrahedral unit. It is also well known that the addition of metal oxides like alkali, alkaline earth or heavy metal oxides in binary, ternary and quaternary borate network based glasses results in similar transformations [17][18][19][20][21]. For higher PbO concentrations, increasing numbers of lead atoms act as glass formers and the coordination of Pb with oxygen neighbors decreases from 8 to 3, as revealed by recent 11 B and 207 Pb MAS NMR studies on lead borate glasses [22].…”

“…The dependence of the boron coordination number in borate glasses and melts as a function of glass composition [17][18][19][20][21] and temperature [23][24][25][26][27] can be highly informative. Unlike silicates, borate glasses consist of boron-oxygen coordination numbers of three and four, and various mechanical, thermal, optical and electrical properties of borate glasses depend critically on the fraction of tetrahedral boron units dispersed throughout the glass network [17][18][19][20][21].…”

“…Unlike silicates, borate glasses consist of boron-oxygen coordination numbers of three and four, and various mechanical, thermal, optical and electrical properties of borate glasses depend critically on the fraction of tetrahedral boron units dispersed throughout the glass network [17][18][19][20][21]. While pure diboron trioxide glass has only triangularly coordinated boron atoms at ambient pressures, recent experiments show almost all (>95%) of these boron atoms become tetrahedrally coordinated at high pressures [28][29][30][31].…”

“…This technique has now been greatly improved by modern, state of the art, higher magnetic field NMR instrumentation and faster MAS probes, which enable complete resolution of the [3] B and [4] B sites, thus allowing determination of N 4 with greater accuracy and precision [21,22,[31][32][33]. 11 B NMR experiments carried out by Bray and coworkers on lead borates showed that the fraction of [4] B atoms in lead borate glasses increases with the PbO content up to 50 mol%, while further increase in PbO content lowers its value [9][10][11][12][13].…”

Spectral editing in solid-state MAS NMR of quadrupolar nuclei using selective satellite inversion

“…The dependence of the FSG-RAPT enhancement on offset frequency for nuclei with different C q values was also exploited to design the (π/2) CT -RAPT-(π/2) CT and RAPT-(π) CT -RAPT-(π/2) CT schemes, for the selective excitation or suppression, respectively, of nuclei with large quadrupolar couplings [4]. These methods, specifically (π/2) CT -RAPT-(π/2) CT , have been successfully utilized to understand the complex structure of Pyrex r by 11 B NMR [5]. More recently, Smith and Seith [6] used (π/2) CT -RAPT-(π/2) CT to simplify a complex 93 Nb spectrum in a layered perovskite, and, additionally, appended the (π/2) CT -RAPT scheme to QPASS [7] to edit 93 Nb NMR spectrum of KCa 2 Nb 3 O 10 that contains two overlapping niobium sites.…”